The difference between Monocrystalline and Sun-Power is in the surface of the panel. The slightly more expensive Sunpower cells are dimpled to give a greater surface area and for greater efficiency when the sun is low or in diffused light. With sealed seams, they are also entirely waterproof. To charge USB devices (phones, Tablets, Cameras) choose one of the folding solar chargers up to 20w. For greater power requirements, the larger 20w, 60w and 100w folding solar panels are able to charge 12v batteries and run through an inverter. Suitable for boats, Camper vans and off-grid portable power.
Although it is true that the brighter the sunlight (not obscured by glass or shadow) the faster the solar panel can convert energy, these premium solar panel chargers just need direct sunlight to produce constant free daily power.